climb_stairs.py

def climb_stairs(n: int) -> int:
    memo = {1:1, 2:2}
    
    def climb(n):
        if n not in memo:
            memo[n] = climb(n-1) + climb(n-2)
        return memo.get(n)
    
    return climb(n)

climbStairs.go

func climbStairs(n int) int {
    memo := map[int]int{
        1:1,
        2:2,
    }
    var climb func(n int) int

    climb = func (n int) int {
        _, ok := memo[n];
        if !ok {
            memo[n] = climb(n-1) + climb(n-2)
        }
        return memo[n] 
    }
    return climb(n)
}

climbStairs.js

let climbStairs = function(n) {
        memo = {1:1,2:2}
        
        function climb(n){
            if ( !(n in memo)){
                memo[n] = climb(n-1) + climb(n-2)
            }
                
            return memo[n] 
        }

        return climb(n)
};

maximalSquare.py

"""

Given a 2D binary matrix filled with 0's and 1's, 
find the largest square containing only 1's and return its area.

1 0 1 0 0
1 0 1 1 1
1 1 1 1 1
1 0 0 1 0

Output: 4

"""

def maximalSquare(self, matrix: List[List[str]]) -> int: 
    rows = len(matrix)
    if rows:
        cols = len(matrix[0])
    else:
        cols = 0 

    dp = [0] * (cols+1)
    maxsq = 0
    prev = 0 

    for i in range(1,rows+1):
        for j in range(1,cols+1):
            temp = dp[j]
            if matrix[i-1][j-1] == "1":
                min_prev = min(dp[j-1], prev)
                min_cur = min(min_prev, dp[j])
                dp[j] = min_cur + 1
                maxsq = max(maxsq,dp[j])
            else:
                dp[j] = 0

            prev = temp 

    return maxsq*maxsq